Furry meal: A pygmy shrew has fallen victim to a noble orb spider (Steatoda nobilis) in southern England. This makes the mouse the third known vertebrate species on the menu of this invasive poisonous spider. Originally introduced from the Canary Islands, the spider, which is only about one centimeter in size, paralyzes its prey with a strong neurotoxin, wraps it in spider silk and sucks it dry. For the scientists, the incident underscores the threat the invasive species poses to native vertebrates.
At least 39 of the 132 known spider families kill small vertebrates, although some are many times larger than the eight-legged hunters themselves. Their secret weapon: a powerful, paralyzing neurotoxin. With the help of the poison mixture, the spiders even get fish, snakes and frogs into their webs. A vertebrate killer, the so-called noble orb spider (Steatoda nobilis), has also long since spread to Europe. It was probably brought in from the Canary Islands. So far, two of their victims are known: a wood lizard and common bats .
Cold-blooded murder at the bedroom window
But scientists led by Michel Dugon from the University of Galway have now identified another prey animal that is on the menu of the ball spider, which is around one centimeter in size. The victim: a pygmy shrew. The crime scene: a bedroom window in Chichester, southern England. The time of the crime: the morning of August 4, 2022. Co-author Dawn Sturgess observed the “scene of the crime.” According to their descriptions, the mouse was probably still alive when it was already hanging in the spider’s web. But the spider’s neurotoxin rendered her increasingly unable to move.
At some point the spider lifted its prey like a pulley 25 centimeters and wrapped it in silk. Something similar had been observed a few years earlier in the case of the wood lizard. The spider fed on the pygmy shrew for three days before finally dropping the sucked rodent on the windowsill. “This observation shows once again that the Noble Orb Spider is perfectly adapted to take down large prey, combining a powerful venom, extremely strong silk, and complex hunting behavior,” reports Dugon.
A danger to native vertebrates
This is the third case in recent years of a protected vertebrate species being killed by the noble orb spider. But the spider is not only dangerous for lizards, bats and shrews, but potentially also for humans. Their powerful nerve toxin, alpha-latrotoxin, can occasionally result in a hospital stay here too.
Due to the multiple “homicides” over the past few years, Dugon and his colleagues no longer classify the noble orb spider as an occasional but as a habitual vertebrate feeder. That makes them all the more threatening for native vertebrate species. The researchers therefore recommend continuing to monitor this spider species closely. (Ecosphere, 2023; doi:10.1002/ecs2.4422 )